Here is the full list of all 20 Spelunky achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Complete the game with at least two players alive. No shortcuts.
Complete the game without collecting any treasure. No shortcuts.
Obtain 500,000 gold.
Complete the game in under 8 minutes. No shortcuts.
Complete 100% of the journal.
Rescue 10 or more damsels in one game.
Complete the game without using shortcuts.
Complete the game the hard way.
Rescue all 16 hidden characters.
Reach the City of Gold.
Obtain the Ankh.
Kill 12 or more shopkeepers in one game.
Complete the game.
Play Adventure Mode 1000 times.
Win the kapala from Kali.
Reach the Temple.
Complete 50% of the journal.
Reach the Ice Caves.
Reach the Jungle.
Beat the Tutorial.